Parameters

hKey
[in] Handle to a currently open key or one of the following predefined reserved handle values:

HKEY_CLASSES_ROOT

HKEY_CURRENT_USER

HKEY_LOCAL_MACHINE

HKEY_USERS

The enumerated values are associated with the key identified by hKey.

dwIndex
[in] Index of the value to retrieve. This parameter should be zero for the first call to the RegEnumValue function and then be incremented for subsequent calls.

Because values are not ordered, any new value will have an arbitrary index. This means that the function may return values in any order.

lpValueName
[out] Pointer to a buffer that receives the name of the value, including the terminating null character.

lpcchValueName
[in, out] Pointer to a variable that specifies the size, in characters, of the buffer pointed to by the lpValueName parameter. This size should include the terminating null character. When the function returns, the variable pointed to by lpcchValueName contains the number of characters stored in the buffer. The count returned does not include the terminating null character.

lpReserved
[in] Reserved; set to NULL.

lpType
[out] Pointer to a variable that receives the type code for the value entry. The following table shows the possible values for type code.

Value

Description

REG_BINARY

Specifies binary data in any form.

REG_DWORD

Specifies a 32-bit number.

REG_DWORD_LITTLE_ENDIAN

Specifies a 32-bit number in little-endian format. This is equivalent to REG_DWORD.

In little-endian format, a multi-byte value is stored in memory from the lowest byte (the little end) to the highest byte. For example, the value 0x12345678 is stored as (0x78 0x56 0x34 0x12) in little-endian format.

REG_DWORD_BIG_ENDIAN

Specifies a 32-bit number in big-endian format.

In big-endian format, a multi-byte value is stored in memory from the highest byte (the big end) to the lowest byte. For example, the value 0x12345678 is stored as (0x12 0x34 0x56 0x78) in big-endian format.

REG_EXPAND_SZ

Specifies a null-terminated string that contains unexpanded references to environment variables (for example, %PATH%). It will be a Unicode or ANSI string depending on whether you use the Unicode or ANSI functions.

REG_LINK

Specifies a Unicode symbolic link. Used internally; applications should not use this type.

REG_MULTI_SZ

Specifies an array of null-terminated strings, terminated by two null characters.

REG_NONE

No defined value type.

REG_RESOURCE_LIST

Specifies a device-driver resource list.

REG_SZ

Specifies a null-terminated Unicode string.

The lpType parameter can be NULL if the type code is not required.

lpData
[out] Pointer to a buffer that receives the data for the value entry. This parameter can be NULL if the data is not required.

lpcbData
[in, out] Pointer to a variable that specifies the size, in bytes, of the buffer pointed to by the lpData parameter. When the function returns, the variable pointed to by the lpcbData parameter contains the number of bytes stored in the buffer. This parameter can be NULL, only if lpData is NULL.

Return Values

ERROR_SUCCESS indicates success. A nonzero error code defined in Winerror.h indicates failure. To get a generic description of the error, call FormatMessage with the FORMAT_MESSAGE_FROM_SYSTEM flag set. The message resource is optional; therefore, if you call FormatMessage it could fail.

Remarks

To enumerate values, an application should initially call the RegEnumValue function with the dwIndex parameter set to zero. The application should then increment dwIndex and call the RegEnumValue function until there are no more values (until the function returns ERROR_NO_MORE_ITEMS).

The application can also set dwIndex to the index of the last value on the first call to the function and decrement the index until the value with index 0 is enumerated. To retrieve the index of the last value, use the RegQueryInfoKey function.

While using RegEnumValue, an application should not call any registry functions that might change the key being queried.

The key identified by the hKey parameter must have been opened with KEY_QUERY_VALUE access. To open the key, use the RegCreateKeyEx or RegOpenKeyEx function.

To determine the maximum size of the name and data buffers, use the RegQueryInfoKey function.